Diablo III is an action RPG set in the dark fantasy world of Sanctuary. Gameplay focuses on combat and character progression and customization. Players progress through several static and dynamically-generated levels completing quests and fighting monsters to save Sanctuary from evil. Several features have been added or changed to focus on fast progression through levels, including health pickups and a simplified crafting system. Besides the ability to select a class and sex, players may customize their characters' skills using Skill Runes dropped from enemies. Co-operative play is available for the campaign, and Player versus Player combat is available in separate multiplayer modes. Diablo III uses a proprietary physics engine which allows for destructible environments.